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ACE inhibitors: ACE is an acronym for Angiotensin Converting Enzyme. ACE inhibitors are blood pressure medications that are prescribed by your doctor to treat systemic hypertension. Some examples of ACE inhibitors include Accupril®, lisinopril, and captopril. ACE inhibitors are not part of specific PAH therapy, they are used for systemic (“regular”) hypertension and/or left-sided (“regular”) heart failure.

Angina: Chest pain or pressure; angina usually results from not enough blood or oxygen getting to the heart muscle. Typically, angina occurs in patients with coronary artery disease, but it can affect patients with many different types of heart disease including pulmonary arterial hypertension.

Angiogram: A type of catheterization that uses dye injected into the blood vessels to accurately evaluate whether or not the blood vessels are narrowed. Can be done for any vessel of the body.

Anticoagulant medications: A group of medications used to thin the blood and block some of the chemicals that make blood clot. These medications can be given by mouth, by injection, or by intravenous infusion. Some of the common names of blood thinners include Coumadin®, warfarin, Lovenox®, and heparin. Aspirin is also a blood thinner, but works by making the platelets in our blood less “sticky.” Read more about conventional medical therapies

Apnea: Slowing/stopping of breathing, usually during sleep. Always abnormal, and needs immediate attention. Obstructive sleep apnea (OSA) is a disease in which the patient stops breathing for short periods of time during sleep because some part of the airway is blocked. OSA can result in pulmonary hypertension. Treatment for OSA can help PH.

Arginine: An essential amino acid (protein building block of our bodies). Arginine is theorized to help open up pulmonary arteries (vasodilate) by working with a substance called nitric oxide that is present in the pulmonary arteries. There was some thought that patients with PAH may have a deficit of arginine and should take additional arginine as a supplement. A recent study found that the supplement was safe for use, but no benefit was found. Studies on this supplement continue.

Arterial Blood Gas (ABG). A blood test where blood is taken from an artery to measures the levels of oxygen and carbon dioxide. It is used to determine how well your lungs are working.

Ascites:Edema, or build-up of fluid in the abdominal cavity. Can cause fullness and heaviness around your waist, causing clothing to be tighter. Can be treated with diuretics, also known as fluid pills.

Atrial fibrillation: A rapid beat of the atrium, which typically occurs in patients with left-sided heart disease but can also occur in PAH. It is sometimes due to pulmonary diseases or fluid overload. The rapid and irregular beating of the atria results in less blood flow to the ventricles, and therefore the rest of the body, and can cause palpitations, dizziness, lightheadedness and passing out.

Atrial septal defects (ASD): A hole in the atrial septum, the wall that separates the right and left upper chambers of the heart, the atria. The hole allows blood to communicate between these two chambers. See congenital heart disease.

Atrial septostomy: Surgery that creates a small hole between the two upper chambers (atria) of the heart. Can relieve pressure on the right side of the heart and improve blood flow, but can also decrease oxygen levels in the blood.

Atrium: The heart is a pump that consists of four sections, known as chambers. The atria (plural for atrium) sits above the ventricles and pumps blood into the ventricles through heart valves. On the right side of the heart, the right atrium pumps blood through the tricuspid valve into the right ventricle. On the left side, the left atrium pumps blood through the mitral valve into the left ventricle.

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Balloon angioplasty: A procedure in which a balloon catheter is inflated inside an artery (typically a coronary artery) to increase its diameter.

Beraprost: A prostanoid medication in an oral form. It has been approved in other countries for treatment of PAH. Beraprost is still in clinical trials in the U.S.

BiPAP machine: Defined as bi-level positive airway pressure. It is a small machine for the treatment of obstructive sleep apnea and other respiratory diseases. Bi-level means that air is delivered under a specific pressure when you breathe in to help assist an inhaled breath, while a different (smaller) amount of pressure is maintained during exhalation. This holds the airways open to make inhalation on the next breath easier. See also CPAP

BMPR2 gene: The “PH gene.” Its full name is bone morphogenetic protein receptor II and some of its mutations have been found in families that have more than one member with pulmonary arterial hypertension (heritable PAH) and in some patients with no known family history of the disease (sporadic PAH). Read more about heritable PAH

Bradycardia: A slow heartbeat, generally less than 55 to 60 beats per minute.

Bronchiolitis obliterans: A disease of the lung tissue (small bronchial tubes and alveoli), not the blood vessels, usually from an unknown toxic exposure, infection and in chronic rejection after lung transplantation.

-C-

Calcium channel blockers (CCBs): Blood pressure medicines for systemic hypertension. CCBs have been found to decrease pulmonary artery pressures in a small percentage of PH patients. CCBs that may help include nifedipine (Procardia XL®, Adalat®), diltiazem (Cardizem®), and amlodipine (Norvasc®). Be aware that only certain PAH patients benefit from CCBs; in others, CCBs can do a lot of harm. Read more about conventional medical therapies

Cardiac catheterization: The definitive final diagnostic test performed to determine if a patient has pulmonary hypertension. Until a right-heart catheterization is performed, a diagnosis of pulmonary arterial hypertension cannot be made. Read more about diagnositic tests

Right-heart catheterization (RHC) is performed by placing a small catheter (tube) into a vein, usually a vein in the neck or groin. The tube is advanced in the direction of blood flow into the right side of the heart and then into the main pulmonary artery. Once the catheter is in the pulmonary artery, measurements of the blood pressure in the pulmonary artery can be made. Next, advancing the catheter into a pulmonary artery branch allows doctors to estimate the pressure on the left side of the heart. This is called a pulmonary capillary wedge pressure. Read more about common tests in PH

Left-heart catheterization (LHC) is performed in a similar manner except that the catheter is placed into an artery, usually the femoral artery in the groin. The catheter is advanced into the left side of the heart to make measurements of pressures in the aorta and left ventricle. These measurements may indicate the presence of a disease related to the structure and/or function of the left side of the heart. Left-sided heart disease can be a result of smoking, high cholesterol or high systemic blood pressure, which predispose to heart attacks.

Or it can be a result of problems related to the structure and function of the heart valves in the left side of the heart (mitral and aortic valves), or even just a problem with the heart muscle itself (cardiomyopathy). Left-sided catheterizations sometimes use contrast dye to look at the blood vessels supplying the heart (coronary angiogram). Occasionally, your doctor may advise you to have both a right- and left-side heart catheterization to help make a diagnosis and to guide treatment. Read more about common tests in PH

Cardiac output: The total amount of blood the heart pumps per minute. In a healthy person this is about 5 to 6 liters per minute; in someone with severe PH it can be as low as 2 to 3 liters or less. (A human has about 5 liters [roughly 5.3 quarts] of blood inside of their arteries at any one time.)

Cardiopulmonary exercise testing (CPET): A way of determining cardiac and pulmonary function by measuring lung gas (oxygen and carbon dioxide) exchange efficiency. Read more about common tests for PH

Catheter: A hollow flexible tube that is inserted into a body cavity, duct or vessel to allow the passage of fluids. There are many types of “catheters.” Below are descriptions of three specific to PH:

A catheter that is placed in a central vein is called a “central line.” It may also be known as a Hickman catheter, Broviac catheter, or a PICC line. A surgeon may use different areas to place one end of a central line catheter into a vein. It is then advanced it to a larger (central) vein leading to your heart. In PAH, the catheter it is typically used to administer intravenous medications, including epoprostenol or treprostinil.

A subcutaneous catheter is a smaller flexible tube that is placed just under the skin in the fat tissue of the body. It is used to deliver medications. These catheters are usually placed by the patient or caregiver.

A diagnostic catheter, a thin, hollow tube that is used to measure pressures in the heart and blood vessels. See cardiac catheterization.

Centers for Disease Control (CDC): A U.S. government agency that tracks all medical diseases in order to help with prevention and treatment of disease. The CDC publishes a weekly bulletin called Morbidity and Mortality Weekly Report (MMWR), which helps establish how many patients are afflicted with certain diagnoses. Learn more about the CDC

Chronic obstructive pulmonary disease (COPD): A chronic disease characterized by difficulty in breathing due to over inflation of the lung sacs and/or constriction of the tubes leading to the air sacs. Learn more about COPD

Chronic thromboembolic pulmonary hypertension (CTEPH): A form of pulmonary hypertension that is secondary to chronic (long-time) blood clots in the lungs.

Cialis®: An FDA-approved oral treatment of erectile dysfunction. Cialis® is the brand name for tadalafil (the same chemical used in the PAH drug, Adcirca®). See also tadalafil

Cirrhosis: A buildup of fiber-like tissue (scarring) in the liver, usually due to chronic liver disease.

Connective tissue disease (a.k.a. Collagen vascular disease/autoimmune disease): Disorders affecting joints (muscles, bones, tendons, cartilage), and solid organs of the body. Can be the result of an autoimmune (immune system in your body turns against itself) or genetic process (inherited disease). Types associated with PH include SLE (lupus), scleroderma, rheumatoid arthritis, and mixed connective tissue disease. Read more about scleroderma and PH

Congenital heart disease (CHD): A defect of the heart present at birth. The defects can be simple holes in the heart or much more complex defects. Learn more about CHD

Cor pulmonale: Enlargement of the right ventricle of the heart, which can be caused by pulmonary hypertension. Consists of symptoms of right side heart failure and fluid overload.

Coumadin®: The brand name for warfarin. It is a blood thinner prescribed for patients that are at risk of developing blood clots (see CTEPH). It is also given to patients with pulmonary hypertension (typically IPAH patients), as there is some evidence that the blood vessels with high pulmonary pressures can be prone to microscopic clots in their pulmonary blood vessels. Coumadin® can help prevent further clots and existing clots from getting bigger. Read more about conventional medical therapies

CPAP: Defined as Continuous Positive Airway Pressure. It is a small machine for the treatment of obstructive sleep apnea and other respiratory diseases. In obstructive sleep apnea, the airway is “obstructed” due to a patient’s size or changes in the airway anatomy that cause collapse during sleep. The CPAP air pressure helps hold open the airways. See also BiPAP machine

CREST syndrome: CREST is an acronym for calcinosis, Raynaud’s syndrome, esophageal dysmotility, sclerodactyly and telangiectasia. CREST is a form of scleroderma that results in calcium deposits in the skin, Raynaud’s phenomenon, esophageal involvement, swollen fingers with tight skin, and reddened/discolored skin from by blood vessels. Patients with CREST syndrome are known to have a greater risk for developing pulmonary hypertension. Learn more about CREST syndrome

CT or CAT scan: An x-ray image of the inside of your body taken by narrow x-rays beamed at you from several angles and run through a computer to form an image with much greater detail than a single x-ray. It is excellent at evaluating solid organs and therefore is a common x-ray ordered for evaluation of the heart and lungs in patients with pulmonary hypertension. CAT stands for cross axial tomography. Read more about common tests in PH

Cyanosis: A bluish or purplish discoloration of the skin and mucus membranes caused by a lack of oxygen in the blood. It is often seen in the nails, face, lips and tongue.

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Echocardiogram (echo): A test that uses moving pictures produced by ultrasonic waves (sound waves, or ultrasound) bounced off your heart to show its structures and functioning. The echocardiogram also estimates the pressures on the right side of the heart, which may help in the diagnosis and treatment of PAH. The pictures are produced in the same way a fetal ultrasound shows a baby in the mother’s womb. Read more about diagnositic tests

Edema: Swelling caused by fluid in your body's tissues. It usually occurs in the feet, ankles and legs, but it can occur in your entire body. See also ascites

Eisenmenger syndrome: A syndrome that results from a birth defect where a hole in the heart that originally caused red, oxygenated blood to go from the left side of the heart to the right side of the heart and back to the lungs before it had a chance to be pumped to the body. After some time, this extra blood flow to the lungs damages the pulmonary arteries and PAH occurs. Over time, as the resistance in the lung arteries increases due to this damage, blue blood begins to skip going to the lungs and goes straight to the left side of the heart where it is pumped back to the body. See congenital heart disease and cyanosis. Learn more about Eisenmenger syndrome

Embolus (plural, emboli): A clump of something (usually a blood clot) or a bubble that has plugged up a blood vessel. An embolism is the blockage of a vessel by an embolus. It's usually a blood clot that has formed somewhere else and traveled to the lungs. A thrombus is a fibrinous blood clot that obstructs a blood vessel. If a thrombus forms in one place and moves to another, it is called a thrombotic embolus. These are all known as blood clots, and can result in PH.

Endothelin: A chemical made by the endothelium (see below). It causes the smooth muscles in the blood vessel’s walls to constrict (tighten up). PAH patients have too much endothelin in their blood.

Endothelin receptor antagonists:Bosentan (Tracleer®) and ambrisentan (Letairis®) are medications that block endothelin from attaching to the endothelium receptors located in the smooth muscle cells of the pulmonary arteries. This prevents the vessels from tightening up/constricting and helps lower the pulmonary artery pressures. Read more about treatment options

Endothelium: The one-cell thick lining of the blood, lymph channels and the heart. Endothelial cells produce lots of chemical compounds that normally make blood vessel walls relax and dilate. In PAH there is an abnormality in the endothelium, which can result in the blood vessels’ inability to relax and dilate. Abnormalities with the endothelium are one possible cause of pulmonary arterial hypertension.

Enzymes: Organic substances made by cells that can act inside or outside of cells to control the rate of chemical reactions without the substance being changed themselves (an enzyme can help the same process along over and over).

Epidemiology: The study of illness in the population.

Epoprostenol sodium: An FDA-approved intravenous treatment for PAH. It is delivered intravenously through a central line catheter and with a small pump. Epoprostenol sodium is the chemical name for Flolan® and Veletri®. See also prostanoids

Etiology (ee-tee-AWL-o-gee): The cause of something, such as a disease.

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Fibrin: The insoluble protein end product of blood coagulation, formed from fibrinogen by the action of thrombin in the presence of calcium ions. Thrombin acts on fibrinogen to form this insoluble protein called fibrin. (Part of the blood coagulation process.)

Fibrosis: Occurs when inflammation or other irritants cause a build-up of fiber-like tissue (scarring).

Functional classifications for PH: A scale designed to define how sick someone with PH is based on how limited the patient is in his/her daily activities. There are two different scales that doctors use to define limitations:

New York Heart Association (NYHA) scale for all cardiac patients. The scale is from one to four: Class I having no symptoms to Class IV in which symptoms occur at rest. Most PAH patients are diagnosed when they have Class II or III symptoms. Learn more about the NYHA scale

World Health Organization (WHO) classifications are a modification the New York Heart Association (NYHA) categories for generic heart failure to make them specific to PH patients. The scale is also from one to four. The WHO and NYHA classes are very similar. One area where they differ is that if you are prone to fainting, you automatically go into Class IV under the WHO class. Learn more about WHO classifications

- H –

Hemodynamics: The pressure measurements obtained during the right and left heart catheterization. Typically, in PH, hemodynamics refers to pulmonary blood pressures, cardiac output and the calculation of pulmonary resistance, which is a combination of both the pulmonary artery pressure and the cardiac output.

Heritable pulmonary arterial hypertension (HPAH): This term is used when the BMPR2 gene has been identified and/or there is a family history of pulmonary hypertension. It is the new term for what used to be called familial pulmonary arterial hypertension (FPAH). Read more about heritable PH

Hickman catheter: An intravenous line used to administer medication. See also catheter

Human immunodeficiency virus (HIV): An infection that causes the immune system to fail and makes the body prone to infectious organisms that typically would not cause infections. Patients with HIV infection can develop PAH at a rate higher than the general population. The reason is unknown. Read more about HIV and PH

Hypertension: Abnormally high blood pressure.

Hypotension: Abnormally low blood pressure.

Hypoxemia: A low concentration of oxygen in the blood. This condition can make the pulmonary vessels contract and raise pulmonary artery pressure.

Hypoxia: A low concentration of oxygen in the air that is breathed, such as occurs aboard an airliner or high on a mountain.

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Idiopathic: A medical term that is used to describe a disease that has no known underlying cause.

Idiopathic pulmonary arterial hypertension (IPAH): Formerly called primary pulmonary hypertension (PPH). It means pulmonary arterial hypertension where the cause is unknown. It is very rare, with an incidence of approximately 2 to 5 per million worldwide. Read more about types of PH

International normalized range (INR) level: A blood test used to determine how long it takes your blood to clot (how thin the blood is). It is used to determine how much Coumadin®/warfarin to prescribe to a patient to help keep the blood thin.

Intravenous (IV): Literally “inside the vein.” Used to designate fluids or medications administered via a catheter or needle placed into the vein. An intravenous administration is called an infusion.

Ischemia: A localized, temporary reduction in blood flow resulting in tissue/organ damage. In cardiac ischemia, blocked blood flow results in chest pain and can result in a heart attack. Ischemia can happen in any organ/tissue of the body.

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Magnetic resonance imaging (MRI): An imaging technique that uses a strong magnetic field and low-energy radio waves to make pictures of the inside of the body. MRI images usually have great detail, and can allow doctors to make some diagnoses much easier. In PH, MRI is currently being used to capture better pictures of the heart, heart valves and the functioning of the heart than seen on an echocardiogram. Sometimes used with radiopaque dye. Read more about common tests in PH

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National Heart, Lung, and Blood Institute (NHLBI): A government institute that is part of the National Institutes of Health. The NHLBI coordinates basic research, clinical investigations and trials, observational studies, and education projects related to the causes, prevention, diagnosis, and treatment of heart, blood vessel, lung and blood diseases as well as sleep disorders. PHA interacts with the NHLBI through the agency’s Public Interest Organizations group. Learn more about the NHLBI

National Institutes of Health (NIH): The National Institutes of Health, a part of the U.S. Department of Health and Human Services whose mission is “to seek fundamental knowledge about the nature and behavior of living systems and the application of that knowledge to enhance health, lengthen life, and reduce the burdens of illness and disability.” Learn more about the NIH

Nebulizer: A machine that can aerosolize (change into small particles) medications so that they can be inhaled.

Nitric oxide (NO): A potent vasodilator in gas form. (Not the same thing as nitrous oxide, which is “laughing gas” used during dental procedures.) It is delivered through a face mask or nasal cannula like oxygen. It has been approved by the FDA for use in newborn babies with persistent pulmonary hypertension. It is being used experimentally for adults with PAH.

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Oximeter/pulse oximeter: A device to measure the concentration of oxygen in your blood by measuring the color in your skin (usually finger or earlobe). Normal saturation is around 97 to 100 percent. In patients with lung disease, it is generally desirable to be above 90 percent “saturated.” Some patients with congenital heart disease have to live with saturations less than 90 percent, since oxygen supplementation does not usually increase their saturation.

Oxygen: An essential element that is needed to sustain life. Oxygen, or O2, is often given as inhaled gas to patients when their oxygen level in the bloodstream is low. Low oxygen occurs with lung disease (PAH, COPD, pneumonia, etc.) and when there is low oxygen content in the air such as at high altitude. Read more about conventional medical therapies

Oxygen saturation (or sat): A measurement of how much oxygen is in the blood. Also called “O2 sat.”

-P-

Palpitation: A sensation of rapid, skipped or pounding heartbeats. Sometimes more noticeable when sitting quietly.

Pathogenesis: The origin and development of a disease

Persistent pulmonary hypertension of the newborn (PPHN): Occurs when a newborn’s arteries to the lungs remain constricted after delivery, cutting down on blood flow to the lungs and resulting in PH. PPHN is treated with inhaled nitric oxide. Learn more about PPHN

Phosphodiesterase (PDE-5) inhibitors: A type of medication that inhibits (blocks) the enzyme phosphodiesterase (PDE-5). PDE-5 breaks down a molecule called cyclic GMP (cGMP). cGMP is the “messenger” of nitric oxide (NO) that causes vasodilation (opening up of the blood vessels). Blocking the breakdown of cGMP then leads to more NO effects. These medications, including sildenafil (Viagra®), tadalafil (Cialis®) and vardenafil (Levitra®), were first used to treat erectile dysfunction. Brand name drugs Revatio® (sildenafil) and Adcirca® (tadalafil) are the only PDE-5 mediations specifically approved for the treatment of PAH. Read more about treatment options

Prostacyclin: A substance made by our bodies that helps regulate blood vessel “tone” by dilating the blood vessels. It is particularly active in the blood vessels of the lungs and is found to be in very low amounts in patients with PH. It is because of this fact that scientists first thought that the addition of man-made prostacyclin (epoprostenol) to the blood by infusion or inhalation could result in vasodilation of the pulmonary arteries. They were correct! The study of epoprostenol infusion for PH in the 1980s and early 1990s proved helpful to PH patients and led to its approval in 1995. As it turns out, in addition to being a vasodilator, prostacyclin may inhibit the growth and thickening of the pulmonary vessel walls, and make platelets less “sticky,” both very good things for treating PH. You may not know … The name prostacyclin comes from the prostate gland because prostaglandin was first isolated from seminal fluid and was thought to have been made by the prostate! Read a brief note about blood vessels

Prostanoids: Prostanoids are a family of chemicals normally made in the body that help regulate blood vessel tone (see above). Members of the prostanoid family of drugs are chemically very similar to one another (they are analogs). Prostacyclin is a type of prostanoid. Present prostacyclin analogs (commonly referred to as prostanoids) include epoprostenol sodium (Flolan®), treprostinil sodium (Remodulin®), generic epoprostenol, room-temperature stable epoprostenol (Veletri®), iloprost (Ventavis®), and inhaled treprostinil (Tyvaso®). These prostacyclin analogs help many PH patients by dilating blood vessels, reducing clotting, slowing down the growth of smooth muscle cells, and improving cardiac output. Although they are all in the same class of drugs, chemically they are not identical, and their toxicity, side effects and effectiveness may differ. Read a brief note about blood vessels

Pulmonary artery: The blood vessels carrying blood from the right ventricle of the heart to the lungs, where the blood is oxygenated. It starts out as the main pulmonary artery, then branches into the right and left pulmonary arteries feeding the right and left lungs, respectively, then continues to branch into smaller and smaller blood vessels, eventually becoming capillaries that exchange oxygen (O2) and carbon dioxide (CO2)with the alveoli (air sacs).

Pulmonary artery pressure (PAP): A measurement of the blood pressure in the pulmonary artery. It has a systolic (upper) and diastolic (lower) component. This is written like a traditional blood pressure measurement. An example for PH is a pulmonary artery pressure 90/40. See mean pulmonary artery pressure. See also mean pulmonary artery pressure

Pulmonary arterial hypertension (PAH): Pulmonary arterial hypertension (PAH) is more specific than the general term “pulmonary hypertension” (see pulmonary hypertension below). PAH is high blood pressure in the pulmonary arteries from disease of the medium- and small-sized vessels of the lung, causing them to narrow and decrease blood flow. Read more about types of PH

Pulmonary function tests (PFTs): A series of tests to find out how much air your lungs can hold, how well they move air in and out, and how well they exchange oxygen. You breathe into a device called a spirometer, or flow meter. The tests can help diagnose some conditions that cause PH. Read more about diagnositic tests

Pulmonary thromboendarterectomy (PTE): A surgical procedure to remove a blood clot (or clots) in the pulmonary arteries in the lungs.

Pulmonary vascular resistance (PVR): A measure of how difficult it is for the heart to pump blood through the lungs. PVR is a calculation obtained during cardiac catheterization. The PVR is often very high in patients with pulmonary hypertension.

Pulmonary vein: The blood vessel returning oxygenated blood from the lungs back to the left side of the heart.

Pulmonary venous hypertension: A condition in which blood flow through the left side of the heart is decreased, causing a backup of blood in the pulmonary veins and therefore causing higher pulmonary vein and pulmonary artery pressure. This cause of this disease is not in the pulmonary arteries, and therefore is not usually treated with drugs designed to treat PAH.

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Raynaud's phenomenon: When fingers get blue and cold easily, and sometimes painful because of blood vessel spasms. Persons with PAH can also have Raynaud’s phenomenon. It is also associated with autoimmune disorders. Learn more about Raynaud's phenomenon

Right atrial pressure: The pressure in the right atrium of the heart. Usually the right atrial pressure is less than 5 mmHg. Elevated right atrial pressure is a sign of right-heart failure and too much fluid in the body.

Right ventricle: The chamber of the heart that pumps un-oxygenated blood through the pulmonary arteries into the lungs. In PH patients, this chamber is often enlarged, its walls are thickened, and its ability to contract is reduced.

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Sarcoidosis: A disease in which swelling (inflammation) occurs in the lymph nodes, lungs, liver, eyes, skin or other tissues. In the lungs it can form granulomas (small areas of inflammation due to tissue injury) and fibrosis (scarring), which can cause PH. Learn more about sarcoidosis

Scleroderma: A progressive and possibly fatal disease in which the body's tissues slowly harden. In some persons, only the skin is affected; in others, even the internal organs harden, including the lungs. It is not known what causes it but there is a genetic component, and it is more common in women than in men. Scleroderma is a common cause of both PH and sometimes PAH. Read more about scleroderma and PH

Sickle cell anemia: A genetic disease in which the red, normally round blood cells of the body form different shapes (sickle shape). This may result in severe joint pain, low oxygen states, chest pain, and PH due to the fact that the abnormally-shaped red blood cells cannot flow through the arteries and veins normally. Patients with sickle cell disease require frequent blood transfusions and pain medications to manage their disease. Read more about sickle cell disease and PH

Six-minute walk test (6MWT)/six-minute walk distance (6MWD): A measurement of how far you can walk in six minutes, including your oxygenation and how short of breath you are at completion. Six-minute walk tests are often used as a measure of whether your PH is improving or worsening. Read more about common tests in PH

Specialty pharmacy: These are special pharmacies developed by regular pharmacies usually to dispense high-cost medications, infusion medications that are complicated to manage, and medications for rare diseases. Specialty pharmacies have a better understanding of a patient’s disease, and have specialized medical staff who can instruct patients how to use specialty medications. Read more about specialty pharmacies

Subcutaneous: Beneath or under all the layers of skin. Some PAH medications are delivered “subcutaneously.”

Syncope: Fainting because of a temporary insufficiency of blood to the brain.

Systemic: Something that affects the body generally rather than just affecting one of the body’s parts.

Systemic lupus erythematous (SLE): A progressive autoimmune inflammatory disease of connective tissue. Its cause is unknown and it is often fatal. A skin rash is often present that spreads across the face in a butterfly wing pattern. The disease often involves the heart and lungs. It is associated with PAH (patients with SLE are much more likely to get PAH than people in the general population — the general incidence of IPAH is only one or two in a million). Also known as lupus.

Systole: The period when your heart is contracting and squeezing blood out. Systolic pressure is the top, higher number in your blood pressure. See also diastole

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A brief word about blood vessels: In our blood vessels, there is a balance between constriction (closing) and dilation (opening) so that blood flow through the blood vessels can be regulated. Blood vessel tone has to do with how much constriction and dilation is going on in the blood vessel at a given time. Constriction of a blood vessel is called vasoconstriction, and dilation of a blood vessel is called vasodilation.

Ventricle: Cavity or chamber in the body. In PH, ventricle generally refers to either of the two lower chambers of the heart that receive blood from the atria (top chambers of the heart) and pump the blood to the lungs (right ventricle does this), or to the body (left ventricle does this).

VO2: A measure of the amount of oxygen (O2) that the body takes in (and thus uses). Doctors measure peak VO2 during exercise; the higher the number, the better the ability of your heart and lungs to deliver oxygen to your body. It is measured in milliliters of oxygen per minute.

Ventilation/perfusion, or V/Q scan. Involves two types of scans: a ventilation scan shows where air flows in the lungs and a perfusion scan shows where blood flows in the lungs.

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